Hexafluoro-2,3-bis(trifluoromethyl)-2-butene (HFBTB) is a known compound which is useful as an environmentally acceptable solvent as a replacement for those applications in which 1,1,2-trichloro-1,2,2-trifluoroethane has been used. HFBTB is also useful as a refrigerant and is further useful as an intermediate to hexafluoroacetone by oxidation.
HFBTB has been prepared by the liquid phase fluorination of 2-chloroperfluoropropene with elemental fluorine followed by dechlorination of the resulting dimer addition product with zinc (W. T. Miller et al., Ind. & Eng. Chem. Vol. 39, 401 1947). This preparation suffers from the disadvantage of the need for expensive fluorine and the attendant disadvantage of a low temperature, liquid phase batch operation with low conversions and yields.
It is accordingly an object of the invention to provide a novel gas phase method for making HFBTB by a gas phase reaction susceptible of continuous operation which does not suffer from the above-noted disadvantages of the prior art method.
Other objects and advantages of the invention will become apparent from the following description.